Page:Scientific results HMS Challenger vol 18 part 2.djvu/801

Rh 3. Polypetta tabulata, n. sp. (Pl. 116, figs. 2, 2a, 2b).

Porospathis tabulata, Hæckel, 1879, Sitzungsb. med.-nat. Gesellsch. Jena, Dec. 12.

Shell subspherical, with elegantly panelled or tabulate surface, composed of small triangular plates, which are separated by a network of prominent crests; at each nodal point of the network a small conical thorn arises (figs. 2a, 2b). Each triangular plate seems to contain a hollow alveole, which opens into the shell-cavity (?). On the surface of the shell are scattered numerous (thirty to forty or more), cylindrical, hollow, radial spines, which are straight or slightly curved, not distinctly alveolate, and increase in size towards the mouth. The aboral spines are scarcely one-third as long as the radius of the shell, whilst the oral spines are three times as long as its diameter. The proboscis of the constricted mouth is a hollow cylinder, longer than the shell-radius, and armed with a corona of fifteen to twenty slender bristle-shaped teeth. The position of this singular species in this family is doubtful.

Dimensions.—Diameter of the shell 0.1 to 0.11, length of the peristome 0.07, breadth 0.02.

Habitat.—Central Pacific, Station 271, depth 2425 fathoms.

4. Polypetta mammillata, n. sp. (Pl. 116, figs. 1, 1a).

Porospathis mammillata, Hæckel, 1879, Sitzungsb. med.-nat., Gesellsch. Jena, Dec. 12.

Shell subspherical, densely covered with numerous mammiliform hollow papillæ, between which are scattered single longer, hollow, radial spines; these are irregularly curved, cylindrical, without distinct alveoles; the twelve longest are two to three times as long as the shell, divergent in the oral direction, and surround the base of the peristome in two irregular alternate circles, each with six spines. The hollow papillæ of the surface, between which are placed numerous circular pores (or dimples?), open into the shell-cavity by a small pore (fig. 1a); they are perhaps reduced radial spines. The constricted peristome is conical and prolonged into an inversely conical proboscis, which is about as long as the radius of the shell; its dilated mouth is surrounded by a corona of slender, divergent, bristle-shaped teeth. The position of this species in the family Medusettida is doubtful; perhaps it is more closely allied to the Castanellida.

Dimensions.—Diameter of the shell 0.12; length of the proboscis 0.08, breadth 0.03; length of the shorter spines 0.1, of the longest spines 0.3.

Habitat.—North Pacific, Station 252, surface.

Castanellida, Haeckel, 1879, Sitzungsb. med.-nat. Gesellsch. Jena, Dec. 12, p. 5.

Definition.— with a spherical or subspherical shell, exhibiting ordinary lattice-work, with circular or roundish pores. Radial spines without circles of basal pores. Mouth of the shell large, usually circular and armed with teeth. Central capsule excentric, placed in the aboral half of the shell-cavity.